How to Grow Lilacs

Lilacs: Colorful, Fragrant, and Easy to Grow

Lilacs are among the most popular garden plants—and for good reasons. Besides being easy to grow, the variety of plant sizes, flower colors, and bloom times creates a colorful and fragrant display over many weeks in the spring. Once they are established lilac plants can grow for hundreds of years.

In the United States, lilacs grow best in the northern states because they need a cold period each year. They prefer full sun and well-drained soil that is slightly acid or alkaline. While lilacs need very little care, they do need watering in times of drought.

Popular Lilac Types

French lilacs (also called common lilacs) grow about fifteen feet tall in clumps eight to twelve feet wide. They have large clusters of flowers and are available in varieties with pink, white, yellow, purple, bronze, or variegated flowers. Korean lilacs grow eight to ten feet tall in a rounded form with small leaves and extremely fragrant flowers. True to their name, tree lilacs grow into medium-size trees rather than shrubs.

Pruning Lilacs

To ensure heavy flowering year after year, remove the flowers after they bloom before they go to seed. Prune out dead branches and suckers in spring after the plants flower. When lilac plants become leggy they need to be pruned. Rather than pruning back the stems, remove about one-third of the oldest and weakest stems at ground level each year for three years. Vigorous new stems will shoot up from the base of the plant.

Lilac Pests and Diseases

Lilac borers are the most serious insect pests; they bore small holes in branches a foot or two above the ground. Small brownish-gray bumps on the branches are oyster-shell scale, which can be controlled by removing badly infested stems then spraying with dormant oil. Powdery mildew is a fungal disease that creates whitish blotches on the leaves, usually in late summer, especially when it’s very humid. It’s unsightly but does not harm the lilac plants.

Lilac Propagation

Once a lilac bush starts to spread you can create new bushes by making a vertical cut with a spade and separating off clumps with several stems each. The new plants will bloom in four or five years.

Want to learn more about growing lilacs?

If you live in the north and have sun and well-drained soil, you will have great success growing lilacs. In warmer areas look for varieties that are suited to your climate. Learn more about growing lilacs at these sites:

Find out about lilacs and lilac celebrations at the Arnold Arboretum, where over 400 lilac plants grow.